Radiation detector of elongated length with electrode support assembly therefor

ABSTRACT

A radiation detection device having a plurality of tubular concentric electrode assemblies positioned end to end within a housing wherein the tubular electrode assemblies are supported by an electrode support assembly comprised of a plurality of electrode support members positioned at the ends of the tubular electrode assemblies so as to space the concentric electrodes and also provide insulation therebetween. The electrode supports are also provided with a plurality of extending ball-like members from the outer periphery of the electrode supports resiliently mounted within the electrode support to accurately position the electrode assemblies within the housing, provide good electrical contact between the housing and the electrode support and also permit ease of removal of the entire assembly from the housing without damage to the components or casing.

ite States Patent s616116 1451 May 7, 1974 [54] RADIATION DETECTOR OF ELONGATED LENGTH WITH ELECTRODE SUPPORT [57] ABSTRACT ASSEMBLY THEREFOR Inventor: Youston M. Sekella, Elmira Hgts.,

Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Oct. 25, 1972 Appl. No.: 300,619

Us. c1. 313/61 R, 313/250, 313/256, 313/257 1m. c1. H015 39/32 riem of search 313/61, 61 D, 25o, 256, 313/257 Primary Examiner-Roy Lake Assistant Examiner-Darwin R. Hostetter Attorney, Agent, 0r Frm-C. F. Renz A radiation detection device having a plurality of tubular concentric electrode assemblies positioned end to end within a housing wherein the tubular electrode assemblies are supported by an electrode support assembly comprised of a plurality of electrode support members positioned at the ends of the tubular electrode assemblies so as to space' the concentric electrodes and also provide insulation therebetween, The electrode supports are also provided with a plurality of extending ball-like members from the outer periphery of the electrode supports resiliently mounted within the electrode support to accurately position the electrode assemblies within the housing, provide good electrical contact between the housing and the electrode support and also permit ease of removal of the entire assembly from the housing without damage to the components or casing.

6 Claims, 4 Drawing Figures SHEE 1 UF 2 FIG.

l f25 l RATENTEU MAY 'I 19M JMENTEDM 7 1914 SHLET 2 UF 2 RADIATION DETECTOR OF ELONGATED LENGTH WITH ELECTRODE SUPPORT ASSEMBLY THEREFOR BACKGROUND OF THE INVENTION In certain applications of neutron detectors within reactor cores, it is sometimes desirable to provide an ionization chamber which has a length substantially the full height of the core. The ionization chamber may be l feet in length. It also may be desirable to divide the sensitive length into two -foot sections with each section having a separate signal cable. Thus the signal from each section may be monitored independently or the sections may be connected in series to provide a signal proportional to the integral of the flux over the full sensitive length of the chamber.

The neutron detector normally consists of two concentric tubular electrodes positioned within a tubular casing with suitable neutron sensing material provided on one or all of the electrodes and the inner surface of the housing or casing. A suitable ionization gas such as nitrogen may be provided within the interior of the casing. The normal practice is to provide a plurality of tubular electrode assemblies approximately 2 feet in length and position the electrode assemblies end to end within the casing so as to provide the desired length. An electrode support member is normally provided between the ends of the electrode assemblies to support and insulate the tubular electrodes within the casing and also to provide an electrical connection, if desired between adjacent ends of electrode assemblies. An electrode support assembly is provided at each end of the entire assembly. The casing is normally at ground potential and at least a portion of the electrode assemblies are also at ground potential to provide a guard shield between the two concentric electrodes at the end regions thereof. It is desirable that these electrode support members permit easy insertion and removal of the assembly without damage to the assembly or the casing. lt is also desirable that the electrode supports provide good electrical connection to the casing.

SUMMARY OF THE INVENTION A radiation detector having a plurality of tubular concentric electrode assemblies positioned end to end with an electrode support member positioned at the end of the electrode assemblies to support and position the electrode assemblies within a housing member. The electrode assemblies and supports provide a unitary assem bly for ease of insertion into the housing, a plurality of ball-like members located on the outer periphery of the electrode support members to locate the electrode assemblies concentrically within the housing to provide adequate spacing between a high voltage electrode member of the electrode assemblies and the housing and also provide electrical contact between the housing and the electrode support members.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be had to the preferred embodiments, exemplary of the invention, shown in the accompanying drawings, in which:

FIG. l is a longitudinal view of a neutron detector partially in section embodying the present invention;

FIG. 2 is an enlarged sectional view of a portion of FIG. l;

FIG. 3 is a view along line III-III of FIG. 2; and FIG. 4 is a detailed sectional view of a spring loaded ball-like bearing member assembly of the electrode support member illustrated in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring in detail-to FIG., l, a neutron detector is illustrated comprising a tubular housing member l0 of a suitable electrical conductive material such as alumi num. The diameter of the housing may be about 2.904 inches and the length about l0 feet. A bottom cap member 14 of a suitable material such as aluminum, closes off the bottom end of the housing member 10. A top cap member 16 which may also be aluminum, closes off the other end of the housing l0. The cap members 14 and 16 may be welded to the housing 10. A high voltage electrode coaxial connector 18 extends through the top cap 16 and signal electrode coaxial connectors 20 and 22 also pass through the top cap 1.6.

A unitary assembly 24 comprised of electrode assemblies 25 and electrode support members 26, 28 and 30 is positioned in the housing 10. The'electrode support members 26, 28 and 30 include three intermediate electrode support members 28, a bottom support electrode support member 30 and a top electrode support member 26. The four electrode assemblies 25 each include an outer tubular high voltage electrode 32 and an inner tubular signal electrode 34. A first electrode assembly 25 is positioned between the top electrode support member 26 and one of the intermediate electrode support members 28. A second and third electrode assembly 25 is positioned between the intermediate electrode support members 28 and the fourth electrode assembly 25 is positioned between the bottom support electrode member 30 and one of the intermediate electrode supports 28. In this manner, four electrode assemblies 25 consisting of the signal electrode 34 and the high voltage electrode 32 are positioned along the length of the housing and may be insulated from or electrically interconnected by means of the electrode support members 26, 28 and 30. In the specific embodiment shown, the outer high voltage electrodes 34 are interconnected along the length of the housing l0. The upper two signal electrodes 34 are interconnected and in turn connected to the external lead 22. The lower two signal electrodes 34 are interconnected and are connected to external lead 20 by means of an internal lead 36. In this manner, a signal representative of radiation in the upper section of the housing 10-may=be derived from the lead 22 while a signal representative of radiation in the lower half of the housing may be derived from the terminal 20. If desired, the two terminals 20 and 22 may be connected externally in order to derive a signal representative of the entire length of the detector.

The electrode support members 26, 2 8, and 30 and the electrode assemblies are secured and locked together by means of a tension rod 38 secured to the top support member 26 by welding and thenprovided with a threaded portion on the lower end of the tension rod 38 so that a nut 40 may be mounted thereon so as to tighten the entire assembly into the unitary assembly 24 prior to insertion into the casing 10. The assembly operation is relatively simple in that the tension rod 38 is inserted into a central opening 42 in the top electrode support assembly 26 and welded thereto. The electrodes 32 and 34 may then be positioned on the top electrode support member 26 and so on down the line until the bottom electrode support member 30 is posi tioned on the rod 38 and then the assembly 24 secured by the nut 40 tightened onto the tension rod 38.

Referring now to FIGS. 2 and 3 a more detailed view of an intermediate electrode support member 28 is shown with associated electrodes 32 and 34. The electrode support member 28 is comprised of a disc support body member 50 ofa suitable material such as aluminum provided with a centrally located aperture 52 through which the tension rod 38 passes. An upper and lower insulator ring 52 ofa suitable material such as ce` ramic is brazed respectively to the upper and lower surface of the support body 50 and provides an insulator with voltage electrodes 32. An upper and lower high voltage electrode positioning ring 56 is provided on the upper and lower surfaces of the body 50 and specifically on the insulating ring 52. The high voltage electrode positioning rings 56 are also of a suitable electrically conductive material such as aluminum and are brazed to the high voltage insulator rings 54. One end ofa high voltage electrode 32 is seated on the high voltage end rings 56.

The signal electrode 34 is similarly supported on the body 50 by means of an upper and lower insulator ring 58 brazed to the aluminum body 50 and ofa smaller diameter than the high voltage insulator rings 54. The rings 58 are concentric to the rings 54. A signal electrode positioned ring 60 of suitable electrical conductive material such as aluminum is provided on the upper and lower surfaces of the body and specifically on the insulating rings 58. One end ofa signal electrode 34 of a suitable electrical conductive material such as aluminum. are seated on the signal electrode positioning ring 60.

Electrical connection may be provided between the upper and lower high voltage electrode end rings 56 by means of a conducting wire 62 which passes through an opening 64 in the body 50 with an insulating sleeve 66 provided within the opening 64 which passes from the upper to lower surface of the body 50. Openings are also provided in the insulating rings 54 and the end rings 56 for the connector wire 62. A fastening screw 66 may be secured into both end rings 56 to secure the connector wire 62 to the upper and lower high voltage electrode rings 56 to electrically interconnect the rings 56. Similarly, an electrical conductive lead 70 may be provided through an opening 72 in the body 50 and the associated insulator ring 58 and end rings 60 for the inner connection between the upper and lower signal electrode rings 60. An insulating sleeve 74 may be provided in the opening 72 of the body 50 to provide insulation between the electrical connector 70 and the body 50. A fastening screw 76 may be utilized to secure the electrical connector 70 to the upper and lower signal electrode end rings 60. lf interconnection is not desired` the electrical connectors 62 and 70 may be omitted during the assembly operations.

The diameter of the body member 50 may be about 2.718 inches leaving a radial clearance between the outer peripheral surface of the body 50 and the inner surface of the housing l of about 0.093 inch. Four radially equally spaced ball members 80 ofa suitable material such as stainless steel, are provided about the outer periphery of the body member 50. The ball members 80, having a diameter of about 0.375 inch, are provided within an opening 82 within the outer surface of the body member 50 as illustrated in FIG. 4. The depth of the opening 82 is about 0.850 inch. The opening 82 includes an inner portion 84, an outer portion 86 having a larger than the inner portion 84 and a tapered portion 88 connecting the two regions 84 and 86. The depth of the portion 86 is about 0.26 inch. A compression spring member 90 is provided within the inner portion 84 of the opening 82. A rivet member 92 having a length of about 0.553 inch is inserted into the spring member 90. The lower surface of the head 94 of the rivet 92 bears on one end of the spring 90. The other end of the spring member 90 bears on the bottom of the opening 82. A ball retaining member 96 of electrical conductive material is driven into the portion 86 of the opening 82 and retains the ball member 80 therein. An interference fit between the outer surface of the retainer member 96 and the surface of the portion 86 retains the retainer member 96 therein. The ball member extends from the outer surface for a distance of about 0.127 inch in the unloaded position and may be compressed inwardly for a distance of at least 0.045 inch until the ball 80 is stopped by the lower end of the rivet 92 striking the inner surface of the opening 82. In normal loading the ball is compressed inwardly about 0.035 inch and applies a pressure of about 6 lbs. to the housing l0. A tool is utilized in this assembly operation in order to insure the proper clearances. This operation will deform either the inner surface of the opening 82 or the end of the rivet 92, if necessary, in order to provide the necessary clearance.

ln this manner, the electrode support members 26, 28 and 30 are accurately positioned within the casing l0 and assures concentricity of the electrodes 32 and 34 within the electrode assemblies 25 within the casing l0. lt also insures good electrical contact between the casing l() and the body member 50. Although the ball mounting arrangement has only been described with respect to one of the intermediate support members 28, similar construction is provided with respect to the other support members 28 and the top support member 26 and the lower support member 30.

The facing walls of the electrodes 32 and 34 may be coated with an neutron sensitive material such as enriched Boron -l0 (Bm) and the casing welded, exhausted in a vacuum and filled a suitable gas such as nitrogen at a pressure of about one atmosphere. The high voltage electrode is held at a potential of about 1,000 volts and the signal electrode connected to a suitable current measuring instrument such as a mieroammeter. The casing is normally held at ground potential.

During operation, a neutron entering the detector 10 interacts with the B10 on the walls of the electrodes 32 and 34 in accordance with the equation Bl0 n a l- Li1 Energy'Either the a or Li7 particles which are ionized is ejected into the gas and produces ionization of very high density along its path. The resulting ionization is then collected at the signal electrode 34 and the high voltage electrode 32 producing a current flow. This signal current is proportional to the incident neutron flux.

Although the present invention has been described with a certain degree of particularlity it should be understood that the present disclosure has been made only by way of examples and numerous changes may be resorted to without-departing from the spirit and scope ofthe present invention.

l claim as my invention:

l. A radiation detector comprising a tubular housing member, a series of electrode assemblies longitudinally spaced within said housing, a plurality of electrode support members with an electrode support member positioned between adjacent electrode assemblies and at the ends of said series of electrode assemblies for positioning said electrode assemblies within said housing member, said electrode support members provided with a plurality of ball-like members extending from the outer surface of said electrode support member and engaging the inner surface of said housing member.

2. The detector as set forth in claim l in which said electrode assemblies consist of an inner and outer tubular electrode having a coating of neutron sensitizing material thereon and in which the outer electrodes serve as the high voltage electrode of the detector and the inner electrode serves as the signal electrode of said detector, said electrode support members including electrical conductive means for connecting through said electrode support members adjacent electrode assemblies and Said housing filled with an ionizable gas.

3. A device set forth in claim l, in which said ball-like members are mounted within a ball retention member secured within an opening in the periphery of a disclike body portion of said electrode support member, spring means located on the remote side of said balllike member with respect to said housing member to spring load said ball-like member, a ball stop member also positioned on the remote side of said ball-like member with respect to said housing member to prevent movement of said ball-like member below the outer surface of the body portion said electrode support member.

4. A device as set forth in claim 3, in which said balllike member, said ball retaining member, said spring means, said ball stop member and said body member of said electrode support member are of electrical conductive material so that at least portions of said electrode support member are at the same potential as the housing member.

5. The device set forth in claim 4 in which said electrode assemblies are insulated from the body portion of said electrode support member by means of annular insulating rings.

6. The device set forth in claim 1, in which said electrode assemblies and said electrode support members are retained together in a longitudinal direction by means of a tension rod member passing through the central region of said assemblies and members are secured to both end electrode support members to place the entire assembly under compression.

l =l =l l= 

1. A radiation detector comprising a tubular housing member, a series of electrode assemblies longitudinally spaced within said housing, a plurality of electrode support members with an electrode support member positioned between adjacent electrode assemblies and at the ends of said series of electrode assemblies for positioning said electrode assemblies within said housing member, said electrode support members provided with a plurality of ball-like members extending from the outer surface of said electrode support member and engaging the inner surface of said housing member.
 2. The detector as set forth in claim 1 in which said electrode assemblies consist of an inner and outer tubular electrode having a coating of neutron sensitizing material thereon and in which the outer electrodes serve as the high voltage electrode of the detector and the inner electrode serves as the signal electrode of said detector, said eleCtrode support members including electrical conductive means for connecting through said electrode support members adjacent electrode assemblies and said housing filled with an ionizable gas.
 3. A device set forth in claim 1, in which said ball-like members are mounted within a ball retention member secured within an opening in the periphery of a disc-like body portion of said electrode support member, spring means located on the remote side of said ball-like member with respect to said housing member to spring load said ball-like member, a ball stop member also positioned on the remote side of said ball-like member with respect to said housing member to prevent movement of said ball-like member below the outer surface of the body portion said electrode support member.
 4. A device as set forth in claim 3, in which said ball-like member, said ball retaining member, said spring means, said ball stop member and said body member of said electrode support member are of electrical conductive material so that at least portions of said electrode support member are at the same potential as the housing member.
 5. The device set forth in claim 4 in which said electrode assemblies are insulated from the body portion of said electrode support member by means of annular insulating rings.
 6. The device set forth in claim 1, in which said electrode assemblies and said electrode support members are retained together in a longitudinal direction by means of a tension rod member passing through the central region of said assemblies and members are secured to both end electrode support members to place the entire assembly under compression. 